NASA says it must tow the Artemis II rocket back to the hangar for repairs

The helium system aboard the SLS upper stage—formally called the Interim Cryogenic Propulsion Stage (ICPS)—worked well in both Artemis II countdown dress rehearsals. “Last night, the team couldn’t establish helium flow through the vehicle. The issue arose during a routine repressurization operation,” Isaacman wrote.

The Space Launch System rocket rolls out of the Vehicle Assembly Building en route to Launch Pad 39B last month.

Credit:
Stephen Clark/Ars Technica

A different molecule, a fresh complication

Helium serves to purge the upper stage engine and pressurize its propellant tanks. NASA said the rocket is in a “safe configuration,” with a secondary system supplying purge air to the upper stage.

NASA saw a comparable failure signature while preparing the first SLS launch for the Artemis I mission in 2022. For Artemis I, engineers traced the issue to a failed check valve on the upper stage that required replacement. According to Isaacman, officials have not yet determined whether Friday’s helium problem resulted from a similar valve failure, an issue with an umbilical interface between the rocket and the launch tower, or a faulty filter.

In any event, technicians cannot access the affected area while the rocket remains on the pad. Inside the VAB, crews will raise work platforms around the vehicle to provide physical access to the upper stage and its associated umbilical connections.

NASA said that beginning rollback preparations now could help managers preserve the April launch window, “pending the outcome of data findings, repair efforts, and how the schedule comes to fruition in the coming days and weeks.”

It remains unclear whether NASA will conduct another fueling test on the SLS after it returns to Launch Pad 39B, or whether technicians will perform additional work on the fragile hydrogen umbilical at the base of the rocket that has caused recurring leaks during the Artemis I and Artemis II campaigns. Managers were pleased with the newly installed seals’ performance during Thursday’s countdown demonstration, but NASA has previously warned that vibrations from transporting the rocket to and from the pad could damage those seals.